/*
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/*
 *    Randomize.java
 *    Copyright (C) 1999 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.filters.unsupervised.instance;

import weka.core.Capabilities;
import weka.core.Instance;
import weka.core.Instances;
import weka.core.Option;
import weka.core.OptionHandler;
import weka.core.RevisionUtils;
import weka.core.Utils;
import weka.core.Capabilities.Capability;
import weka.filters.Filter;
import weka.filters.UnsupervisedFilter;

import java.util.Enumeration;
import java.util.Random;
import java.util.Vector;

/**
 * <!-- globalinfo-start --> Randomly shuffles the order of instances passed
 * through it. The random number generator is reset with the seed value whenever
 * a new set of instances is passed in. <p/> <!-- globalinfo-end -->
 * 
 * <!-- options-start --> Valid options are: <p/>
 * 
 * <pre>
 *  -S &lt;num&gt;
 *  Specify the random number seed (default 42)
 * </pre>
 * 
 * <!-- options-end -->
 * 
 * @author Len Trigg (trigg@cs.waikato.ac.nz)
 * @version $Revision: 1.7 $
 */
public class Randomize extends Filter implements UnsupervisedFilter,
		OptionHandler {

	/** for serialization */
	static final long serialVersionUID = 8854479785121877582L;

	/** The random number seed */
	protected int m_Seed = 42;

	/** The current random number generator */
	protected Random m_Random;

	/**
	 * Returns a string describing this classifier
	 * 
	 * @return a description of the classifier suitable for displaying in the
	 *         explorer/experimenter gui
	 */
	public String globalInfo() {
		return "Randomly shuffles the order of instances passed through it. "
				+ "The random number generator is reset with the seed value whenever "
				+ "a new set of instances is passed in.";
	}

	/**
	 * Returns an enumeration describing the available options.
	 * 
	 * @return an enumeration of all the available options.
	 */
	public Enumeration listOptions() {

		Vector newVector = new Vector(1);

		newVector.addElement(new Option(
				"\tSpecify the random number seed (default 42)", "S", 1,
				"-S <num>"));

		return newVector.elements();
	}

	/**
	 * Parses a given list of options. <p/>
	 * 
	 * <!-- options-start --> Valid options are: <p/>
	 * 
	 * <pre>
	 *  -S &lt;num&gt;
	 *  Specify the random number seed (default 42)
	 * </pre>
	 * 
	 * <!-- options-end -->
	 * 
	 * @param options
	 *            the list of options as an array of strings
	 * @throws Exception
	 *             if an option is not supported
	 */
	public void setOptions(String[] options) throws Exception {

		String seedString = Utils.getOption('S', options);
		if (seedString.length() != 0) {
			setRandomSeed(Integer.parseInt(seedString));
		} else {
			setRandomSeed(42);
		}

		if (getInputFormat() != null) {
			setInputFormat(getInputFormat());
		}
	}

	/**
	 * Gets the current settings of the filter.
	 * 
	 * @return an array of strings suitable for passing to setOptions
	 */
	public String[] getOptions() {

		String[] options = new String[2];
		int current = 0;

		options[current++] = "-S";
		options[current++] = "" + getRandomSeed();

		while (current < options.length) {
			options[current++] = "";
		}
		return options;
	}

	/**
	 * Returns the tip text for this property
	 * 
	 * @return tip text for this property suitable for displaying in the
	 *         explorer/experimenter gui
	 */
	public String randomSeedTipText() {
		return "Seed for the random number generator.";
	}

	/**
	 * Get the random number generator seed value.
	 * 
	 * @return random number generator seed value.
	 */
	public int getRandomSeed() {

		return m_Seed;
	}

	/**
	 * Set the random number generator seed value.
	 * 
	 * @param newRandomSeed
	 *            value to use as the random number generator seed.
	 */
	public void setRandomSeed(int newRandomSeed) {

		m_Seed = newRandomSeed;
	}

	/**
	 * Returns the Capabilities of this filter.
	 * 
	 * @return the capabilities of this object
	 * @see Capabilities
	 */
	public Capabilities getCapabilities() {
		Capabilities result = super.getCapabilities();

		// attributes
		result.enableAllAttributes();
		result.enable(Capability.MISSING_VALUES);

		// class
		result.enableAllClasses();
		result.enable(Capability.MISSING_CLASS_VALUES);
		result.enable(Capability.NO_CLASS);

		return result;
	}

	/**
	 * Sets the format of the input instances.
	 * 
	 * @param instanceInfo
	 *            an Instances object containing the input instance structure
	 *            (any instances contained in the object are ignored - only the
	 *            structure is required).
	 * @return true if the outputFormat may be collected immediately
	 * @throws Exception
	 *             if format cannot be processed
	 */
	public boolean setInputFormat(Instances instanceInfo) throws Exception {

		super.setInputFormat(instanceInfo);
		setOutputFormat(instanceInfo);
		m_Random = new Random(m_Seed);
		return true;
	}

	/**
	 * Input an instance for filtering. Filter requires all training instances
	 * be read before producing output.
	 * 
	 * @param instance
	 *            the input instance
	 * @return true if the filtered instance may now be collected with output().
	 * @throws IllegalStateException
	 *             if no input structure has been defined
	 */
	public boolean input(Instance instance) {

		if (getInputFormat() == null) {
			throw new IllegalStateException("No input instance format defined");
		}
		if (m_NewBatch) {
			resetQueue();
			m_NewBatch = false;
		}
		if (isFirstBatchDone()) {
			push(instance);
			return true;
		} else {
			bufferInput(instance);
			return false;
		}
	}

	/**
	 * Signify that this batch of input to the filter is finished. If the filter
	 * requires all instances prior to filtering, output() may now be called to
	 * retrieve the filtered instances. Any subsequent instances filtered should
	 * be filtered based on setting obtained from the first batch (unless the
	 * setInputFormat has been re-assigned or new options have been set). This
	 * implementation randomizes all the instances received in the batch.
	 * 
	 * @return true if there are instances pending output
	 * @throws IllegalStateException
	 *             if no input format has been set.
	 */
	public boolean batchFinished() {

		if (getInputFormat() == null) {
			throw new IllegalStateException("No input instance format defined");
		}

		if (!isFirstBatchDone()) {
			getInputFormat().randomize(m_Random);
		}
		for (int i = 0; i < getInputFormat().numInstances(); i++) {
			push(getInputFormat().instance(i));
		}
		flushInput();

		m_NewBatch = true;
		m_FirstBatchDone = true;
		return (numPendingOutput() != 0);
	}

	/**
	 * Returns the revision string.
	 * 
	 * @return the revision
	 */
	public String getRevision() {
		return RevisionUtils.extract("$Revision: 1.7 $");
	}

	/**
	 * Main method for testing this class.
	 * 
	 * @param argv
	 *            should contain arguments to the filter: use -h for help
	 */
	public static void main(String[] argv) {
		runFilter(new Randomize(), argv);
	}
}
